Bucket or shallow pan
Use it for: Catches the water and debris that spill out when the old trap comes apart.
Shop buckets for under-sink workUnder-sink plumbing
How to Replace a Sink P Trap Kit
To replace a sink p trap kit, confirm the trap is the leaking or damaged part, put a bucket under the sink, remove the old trap pieces, dry-fit the new kit, tighten the slip joints evenly, and then run water long enough to make sure it drains cleanly without leaks or sewer smell.
A sink p trap kit is one of the more straightforward plumbing parts to replace, but it has to line up correctly. Most problems come from cracked plastic, worn slip-joint washers, corrosion, or a trap that was bumped out of position. Take your time with the fit, and do not force the pipes together.
Before you start: Match the pipe diameter, inlet and outlet configuration, and trap style before ordering.
Safety first
- Wear gloves if the old trap contains dirty water or debris.
- Use caution with pliers on plastic fittings so you do not crack the new parts.
- Keep your face out from directly under the trap when loosening the first connection, since trapped water can spill suddenly.
- If you find hidden rot, mold, or a loose wall drain connection, stop and address that before relying on the new trap.
Tools you may need
Channel lock pliers
Use it for: Helps loosen stubborn slip nuts and snug them without overdoing it.
Find channel-lock pliers
Adjustable wrench
Use it for: Useful if the trap connects to metal fittings or a threaded adapter that needs support.
Shop adjustable wrenches
Rags or paper towels
Use it for: Lets you wipe joints dry so small leaks are easy to spot during testing.
Get shop towels
Tape measure
Use it for: Helps confirm the new trap kit matches the existing pipe size and reach.
Find a tape measureAs an Amazon Associate I earn from qualifying purchases. Repair Riot may earn a commission at no extra cost to you.
Step-by-step fix
Step 1: Confirm the p trap kit is the right repair
- Look under the sink while the basin drains and check where the water is coming from.
- Replace the sink p trap kit if the trap bend, trap arm, slip nuts, or slip-joint washers are cracked, corroded, warped, or leaking at the trap assembly itself.
- Also replace it if the trap was removed for a clog and the old parts no longer seal well when reassembled.
- If the leak is coming from the sink basket, tailpiece higher up, shutoff valves, supply lines, or the wall connection behind the trap, this repair will not solve the root problem.
If it works: You have confirmed the leak, damage, or poor fit is centered on the trap assembly under the sink.
If it doesn’t: Dry everything, run water again, and trace the first point where moisture appears before buying parts or taking the trap apart.
Stop if:
- The cabinet floor, wall, or surrounding wood is soft, swollen, moldy, or badly damaged from a long-term leak.
- The drain stub-out in the wall is loose, broken, or moving when touched.
- You smell strong sewer gas and cannot identify where the drain system is open or damaged.
Step 2: Set up the area and remove the old trap
- Clear out the cabinet so you can work directly under the drain.
- Place a bucket or shallow pan under the trap and keep rags nearby.
- If the sink was just used, let hot water cool so you do not get splashed.
- Loosen the slip nuts at the trap bend by hand first, then use pliers only if needed.
- Lower the trap carefully and let the trapped water drain into the bucket.
- Remove the old trap bend, trap arm, and any old washers that stayed stuck on the pipes.
If it works: The old trap assembly is out and the area is ready for the new parts.
If it doesn’t: If a nut will not turn, support the connected pipe with one hand and work it loose gradually instead of twisting the whole drain assembly.
Stop if:
- A metal drain pipe crumbles, splits, or twists in the wall when you try to loosen the connection.
- The sink tailpiece or wall adapter is cracked or too damaged to seal to a new trap kit.
Step 3: Clean the connections and dry-fit the new kit
- Wipe the sink tailpiece and the wall drain connection clean so the new washers can seat properly.
- Compare the new kit pieces to the old layout and confirm the diameter and general shape match.
- Slide the slip nuts and washers onto the pipes in the correct direction before assembling the trap.
- Dry-fit the trap bend and trap arm so the trap lines up naturally between the sink tailpiece and the wall connection.
- Trim only if the kit is designed to be cut to length and you clearly need a shorter section for proper alignment.
If it works: The new trap kit lines up without forcing the pipes up, down, or sideways.
If it doesn’t: Reposition the trap pieces and check washer direction again. If the alignment is still off, remeasure the pipe size and connection style before continuing.
Stop if:
- The new kit cannot reach both connections without strain or leaves the trap badly misaligned.
- The wall connection or sink tailpiece is out of position enough that the trap cannot be installed squarely.
Step 4: Assemble and tighten the new p trap kit
- Start all slip nuts by hand so the threads do not cross.
- Seat each washer evenly and make sure the trap bend stays centered under the drain.
- Tighten the slip nuts hand-tight first, then give each one a small additional snug with pliers if needed.
- Do not overtighten plastic nuts, because that can distort the washer or crack the fitting.
- Wipe every joint dry when the assembly is fully installed.
If it works: The new trap is installed, supported by its own alignment, and all joints are dry and snug.
If it doesn’t: If a nut feels crooked or binds early, back it off and restart it by hand before tightening again.
Stop if:
- A plastic nut or fitting cracks while tightening.
- The trap assembly only stays together when the pipes are being forced into place.
Step 5: Run water and check for leaks
- Run a slow stream of water first and watch each slip joint closely.
- Then fill the sink partway and let it drain to send a stronger flow through the trap.
- Touch each joint with a dry finger or paper towel to catch small leaks that are hard to see.
- If a joint drips, tighten that slip nut slightly and test again.
- Repeat until the trap stays dry through both a slow drain and a full-basin drain.
If it works: The trap drains normally and stays dry during active use.
If it doesn’t: If a joint keeps leaking, take that connection apart, inspect the washer position, and reassemble it squarely instead of just tightening harder.
Stop if:
- Water is leaking from a different drain part above or behind the trap, showing the original diagnosis was incomplete.
- The sink backs up badly, suggesting a clog farther down the drain line rather than a trap replacement issue.
Step 6: Confirm the repair holds in real use
- Use the sink normally a few times over the next day, including one full-basin drain if possible.
- Check the cabinet floor and the outside of the trap after each use.
- Notice whether any sewer odor returns after the trap has water sitting in it.
- Leave the area under the sink clear until you are sure the repair is staying dry.
If it works: The sink drains well, the trap stays dry in normal use, and there is no sewer smell.
If it doesn’t: If moisture returns after several uses, dry the trap again and pinpoint the exact joint or nearby part that is leaking before making another adjustment.
Stop if:
- Leaks continue even after correct reassembly and washer positioning, which usually means another connected drain part is damaged or mismatched.
Replacement Parts
Find a sink p trap kit on Amazon
Match the pipe diameter, inlet and outlet configuration, and trap style before ordering.
As an Amazon Associate I earn from qualifying purchases. Repair Riot may earn a commission at no extra cost to you.
Verify the repair
- No water appears at any slip joint during a slow drain test.
- A full sink drains without drips, shifting, or gurgling at the trap.
- The trap remains dry after several normal uses.
- There is no sewer odor coming from under the sink.
FAQ
Do I need plumber's tape on a sink p trap kit?
Usually no. Most sink p trap kits seal with slip-joint washers, not thread seal tape. Tape on the slip-nut threads usually does not fix a bad washer or poor alignment.
Why does a new p trap still leak after I tighten it?
The most common causes are a crooked slip nut, a washer facing the wrong direction, dirt on the sealing surface, or pipes that are being forced out of alignment. Take the leaking joint apart and reassemble it squarely.
Can I reuse the old washers with a new trap?
It is better to use the new washers that come with the kit if they match the connection. Old washers often flatten out or harden and may not seal well again.
What if the new trap kit is too long?
Some kits include sections that can be cut to fit, but only trim parts that are meant to be trimmed. Measure carefully first. If the layout is wrong for your sink, exchange the kit for the correct configuration instead of forcing it.
Is a sewer smell always caused by a bad p trap?
Not always. A cracked trap or loose joint can let sewer gas out, but odors can also come from a dry trap, a leak at another drain connection, or a venting or drain problem farther in the system.